You're going to drive to buy illegal drugs, and you don't put your seat belt on, so now some cop has cause to pull you over, what if he's doing it on the way back? Fucking idiot.
When I was a teen driver in the 90s, my rule was seatbelts or get the fuck out. If they fought me on it, I described to them in excruciating detail what my aunt looked like after a semi hit her car and she wasn't wearing a seatbelt. She was unrecognizable as a human being.. and she lived. Imagine looking like that while still alive. Put on your fucking seatbelt.
Where I live, the driver gets the ticket if the passenger has no seatbelt. The car doesn't move unless everyone is buckled in, because I'm not paying for someone else's laziness.
I have done that except at like from <5km/h with a friend who didn't feel like putting it on. Just enough so they are jolted a little forward. That got them to put it on really quickly.